The present invention relates to a waste toner detection mechanism that detects a state in which waste toner has been full in a waste toner container provided in an image forming apparatus, and an image forming apparatus provided with such a waste toner detection mechanism.
When a toner image is formed with toner on a photoreceptor in an electrophotographic image forming process in an image forming apparatus, all the toner is not transferred onto a paper sheet, and toner that has not been transferred remains as waste toner on the photoreceptor. The waste toner is scraped from the photoreceptor and sent to a waste toner container before the following charging process. The image forming apparatus is provided with a waste toner detection mechanism that detects a state in which waste toner has been full in the waste toner container and prompts disposal of the waste toner or replacement of the waste toner container when the waste toner detection mechanism detects a full state of the waste toner.
Some conventional waste toner detection mechanisms have been provided with a floating member that rotates with an increase of the storage amount of waste toner in the waste toner container, a cam member that rotates along with the floating member, and a flag member that is biased upward by a spring (see Japanese Patent Laid-Open Publication No. H09-237020, for example).
According to the waste toner detection mechanism disclosed in Japanese Patent Laid-Open Publication No. H09-237020, the cam member is provided with a slit on the peripheral surface of the cam member, and the flag member is provided with a protruding portion that contacts the peripheral surface of the cam member. The cam member rotates along with floating member with the increase in the storage amount of the waste toner. When the cam member rotates to a position in which the slit faces the protruding portion, the flag member rises by the elastic force of the spring, the protruding portion then fits into the slit, and the light shielding portion of the flag member is exposed and displays the full state of the waste toner. By the elastic force of the spring that acts on the flag member, the light shielding portion continues to display the full state. Since the full state of the waste toner is held on the side of the waste toner container, it is not necessary to store the full state of waste toner on the side of the main body of the image forming apparatus, and thus the load on a control portion is reduced.
However, the waste toner detection mechanism disclosed in Japanese Patent Laid-Open Publication No. H09-237020 needs to be provided with the floating member that rotates with the increase in the waste toner in the waste toner container, which causes a problem that the size of the waste toner container is increased. In addition, since the height of the waste toner in the waste toner container is not uniform, the floating member is capable of only partially detecting the height of the waste toner but is not capable of accurately detecting the collected amount of the waste toner of the entire waste toner container, which easily causes an error in detecting the full state. Further, the waste toner detection mechanism disclosed in Japanese Patent Laid-Open Publication No. H09-237020 maintains the display of the full state by the light shielding portion of the flag member by using the elastic force of the spring, which makes it difficult to cope with large torque that acts on the stirring shaft of a large-capacity toner collection container. In addition, the waste toner detection mechanism disclosed in Japanese Patent Laid-Open Publication No. H09-237020 is not capable of easily releasing the display of the full state by the light shielding portion of the flag member and therefore is not suitable for reuse of the waste toner container.
In view of the foregoing, preferred embodiments of the present invention are directed to provide a waste toner detection mechanism and an image forming apparatus that are capable of accurately detecting the full state of waste toner based on torque that acts on a stirring shaft and achieving the reuse of a waste toner container without incurring the increase in size of the waste toner container.